Blood oxygenator



March 24, 1970 D. L. TOMPKINS 3,502,440

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Y Inventor Dougl L. To kins Arfomzy United States Patent 3,502,440 BLOODOXYGENATOR Douglas L. Tompkins, Evanston, Ill., assignor to BaxterLaboratories, Inc., Morton Grove, Ill., a corporation of Delaware FiledJuly 3, 1967, Ser. No. 650,890 Int. Cl. A61m N03 US. Cl. 23-2585 3Claims ABSTRACT OF THE DISCLOSURE A blood oxygenator of the bubble typeincluding a gas bypass conduit which connects angularly disposed upperand lower sections of a gas stripping chamber arranged for downward flowof oxygenated blood to provide an escape path for undissolved gas, saidgas bypass conduit being S-shaped and having opposite end openingsfacing downstream of the path of blood flow in the gaS strippingchamber.

The present invention relates to oxygenators. More particularly, itrelates to a device adapted as a substitute for a heart and lungs duringsurgery.

Oxygenators with which this invention is concerned are of the well-knownbubble type adapted physically to mix oxygen with venous blood in orderto effect red cell release of carbon dioxide. This is in contrast to thefilm type oxygenator adapted for mass gas transfer across a permeablebarrier which is interposed between gas and liquid phases. Advantages ofbubble type oxygenators are set out in Patent No. 3,087,490 issued Apr.30, 1963, which together with Patent Nos. 3,058,464 and 3,112,746,respectively issued Oct. 16, 1962, and Dec. 3, 1963, disclosesoxygenators for which this invention is adapted.

In addition to providing means for oxygenating blood, a bubble typeoxygenator also necessarily has gas removal means for preventing returnto the body of undissolved gases with oxygenated blood. conventionally,the gas removal means comprises (1) a defoaming chamber adapted toliberate most undissolved gases from oxygenated blood, and (2) astripping chamber which is arranged downstream of the defoaming chamberand is adapted for removal of the remainder of undissolved gases.Because of the requirement for removal of undissolved gases, the rate atwhich blood may be returned to the body after oxygenation is a functionof the rate at which blood can arrive free from undissolved gas at theoutput end of the oxygenator.

According to the present invention, and as an object thereof, animproved bubble type oxygenator is provided.

It is another object of the invention to improve the efficiency of thestripping chamber of a bubble type oxygenator by increasing its rate ofremoval of undissolved gases.

Coincidentally, it is an object of the invention to improve the rate ofblood flow through an oxygenator of the indicated type.

To effect the foregoing objects, a blood oxygenator has a pair offlexible faces joined together along continuous lines to provide a mainconduit which has upstream and outlet ends arranged for blood flow in adownstream direction. The main conduit comprises a vertically extendingoxygenating chamber, a defoaming chamber which is serially connected toand disposed downstream of said oxygenating chamber, and a gas strippingchamber which is serially connected to and disposed downstream of saiddefoaming chamber. The stripping chamber is defined by angularlydisposed upper and lower sections and a curved interconnecting sectionarranged for fluid communication with each other and downward flowtherethrough of blood received from said defoaming chamber. Means areprovided for introducing venous blood and oxygen into the upstream endof said conduit. Additionally, means are provided for venting theconduit. Furthermore, shunting means are provided for rising gas inblood downstream of the defoaming chamber, the shunting means beingdefined by a bypass conduit which is connected in parallel with thestripping chamber across the interconnecting section and arranged forblood flow in a direction different from the direction of flow in themain conduit to prevent trapping of rising undissolved gas in theinterconnecting section.

The foregoing and other objects, features and advantages of the presentinvention will become more apparent upon consideration of the followingdescription and appended claims, when considered in conjunction with theaccompanying drawings wherein the same reference character or numeralrefers to like or corresponding parts throughout the several views.

On the drawings:

FIG. 1 is an elevational view, partially in section, of an oxygenatorembodying the present invention.

FIG. 2 is an enlarged view in section of a portion of the strippingchamber of said oxygenator showing fluid flowing therein.

Referring now more particularly to FIG. 1, there is seen an exemplaryoxygenator generally designated 10 which is formed from a pair ofsimilar translucent sheets 11 (only one of which is shown in thedrawings) arranged in face-to-face lay flat relation. Sheets 11 arefabricated from a flexible polymeric material such as polyvinylchlorideand united by heat seals along a number of lines 19 and 20 to form amain channel or conduit generally designated 12 and adapted for bloodflow. Oxygenator 10 is equipped with a suitable horizontal upper openingfor vertical suspension from a rod 13 of a hanger frame 14 to othercomponents 15 of which the oxygenator may be secured by ties 16 (onlysome of which have been numbered) to secure the oxygenator in a verticalplane.

Blood to be treated is pumped into oxygenator 10 in the upstream orinlet end 17 thereof, while rejuvenated blood suitable for return to abody is removed from main conduit 12 at the downstream or outlet end 18thereof. Blood entering upstream end 17 may come from a vein through aconduit 21 and from a wound or incision through a conduit 22. Bloodentering the oxygenator through conduit 21 will not have been in contactwith air, and suitable pumps (not shown) are employed to maintain suchcondition. The blood sucked from the wound, however, which entersconduit 22, having been contacted with air, may have clots presenttherein thus necessitatingemployment of a filter 23 which is disposed inmain conduit 12 in the path of blood flow. A conduit 24 is arranged forintroduction of a stream of oxygen bubbles into the upstream end 17 ofmain conduit 12, and a conduit 25 is arranged for removal of rejuvenatedblood from the downstream end 18 of main conduit 12. Conduits 21 and 24comprise means for introducing venous blood and oxygen into the upstreamend of main conduit 12.

Main conduit 12 comprises three serially connected chambers, namely, anoxygenating chamber 26, a defoaming chamber 27 and a gas strippingchamber 31. Oxygenating chamber 26, for which upstream end 17 comprisesan entry portion at the lower end of said oxygenating chamber, extendsvertically. Defoaming chamber 27 is disposed downstream of theoxygenating chamber and extends substantially horizontally from theupper end of the oxygenating chamber along the top of said oxygenator.Gas stripping chamber 31 is disposed downstream of said defoamingchamber and is defined by angularly disposed upper and lower sections 32and 33 which are adapted for fluid communication through aninterconnecting curved section 34. As shown in FIG. 1, the strippingchamber terminates in outlet end 18 and is arranged for gravity flowtherethrough of blood received from defoaming chamber 27.

In the exemplary form of the invention, stainless steel sponge packing28 occupies the defoaming chamber to provide a relatively large surfacearea to enhance removal of undissolved gases from blood in said chamber.A vent tube 29 connects the defoaming chamber with the exterior of theoxygenator. A similar tube 30 vents the gas stripping chamber. Tubes 29and 30 comprise means for venting main conduit 12.

The device particularly described to this point is conventional, saiddevice being adapted to receive and oxygenate blood in the oxygenatingchamber from a patient and return the blood in rejuvenated condition tosuch patient from outlet end 18. However, to insure adequate bloodoxygenation, excessive oxygen is introduced into main conduit 12 throughconduit 24. This rises through the blood in the oxygenating chamber asundissolved gas in bubble form and causes foam formation in the blood atthe top of the oxygenating chamber. Undissolved oxygen responsible forthe foam, together with other undissolved gases (if any), is removed indefoaming chamber 27 in accordance with the teachings of the prior art.The defoamed blood passes from the defoaming chamber 27 downwardlythrough gas stripping chamber 31. It is in this latter chamber thatundissolved gas not removed in the defoaming chamber rises throughdownwardly flowing blood for removal from conduit 12 through vent 30. Toinsure that all blood leaving the oxygenator through the conduit 25 isfree from undissolved gas, the rate of flow of blood through theoxygenator, as well as the length of stripping chamber 31, are suitablyadjusted. In this regard, it is appreciated that by increasing thestripping rate in gas stripping chamber 31, the rate at which blood maybe returned to a patient from the outlet end 18 of said strippingchamber may be accordingly increased, all other factors remainingconstant.

While various expedients heretofore have been employed for increasinggas stripping efiiciency for the reason aforesaid, none is as efiicientor effective as the invention herein disclosed. It is defined by abypass conduit 35 which in the exemplary embodiment is S-shaped andcomprises shunting means for rising undissolved gases in blooddownstream of the defoaming chamber. The bypass conduit is connected inparallel with stripping chamber 31 across interconnecting section 34 andis arranged for blood flow in a direction different from the directionof flow in stripping chamber 31 to prevent undissolved gas bubbles frombecoming trapped in the interconnecting section. By providing suchdifferent direction for blood flow, the flow rate in the bypass conduitis greatly decreased from the flow rate in gas stripping chamber 31, asa consequence of which blood flowing in the bypass conduit offers lessresistance to rising gas bubbles than the resistance of blood flowing instripping chamber 31. Accordingly, bubbles will rise through said bypassconduit. To effect the desired flow control of both blood andundissolved gas, bypass conduit 35 has an upstream end 36 with an upperopening 37 which faces downstream in the upper angular stripping chambersection 32 through the lower wall 40 of which fluid communication isestablished. Moreover, bypass conduit 35 at its lower end 38 has adownstream opening 39 which faces downstream in the lower angularlydisposed stripping chamber section 33 through the upper wall 41 of whichfluid communication is established.

As a consequence of the foregoing construction, undissolved gas bubblesin lower angular section 33 will rise toward and move upwardly alongupper wall 41 into downstream-facing lower opening 39 of bypass conduit35. These bubbles will rise in the bypass conduit toward opening 37 inthe direction of arrows 42 (only some of which have been numbered)against the force of blood flowing downwardly in the direction of arrows43. The arrangement of opening 37 is such that rising bubbles are sweptby the relatively rapid flow force in the stripping chamber 31 from theupper end 36 of bypass conduit 35 in the direction of arrows 45. If theopening 37 were to face upstream, escape of gas bubbles rising throughthe bypass would have to overcome the force of blood flow in thedirection of arrows 44 in upper angular gas chamber section 32.

The arrangement according to the invention is such that undissolved gasbubbles are prevented from entering the curved interconnecting section34. Instead, gas bubbles Will rise from upper bypass opening 37 to thetop Wall 46 of angular stripping chamber section 32, and from there moveupwardly for liberation from conduit 12. Be cause the improvedconstruction facilitates removal of undissolved gases from gas strippingsection 31 at a more rapid rate than the gas stripping rate ofheretofore known bubble type oxygenators, the blood flow rate through anoxygenator in accordance with the present invention may be increasedover the rate of flow in oxygenators of like size constructed inaccordance with the prior art.

What is claimed is:

1. In a blood oxygenator of the bubble type having a pair of flexiblefaces joined together along continuous lines to provide a main conduithaving upstream and outlet ends arranged for blood flow in a downstreamdirection, said main conduit comprising a vertically extendingoxygenating chamber, a defoaming chamber serially connected to anddisposed downstream of said oxygenating chamber, and a gas strippingchamber serially connected to and disposed downstream of said defoamingchamber, said stripping chamber defined by angularly disposed upper andlower sections and an interconnecting curved section arranged for fluidcommunication with each other and downward flow therethrough of bloodreceived from said defoaming chamber; means for introducing venous bloodand oxygen into the upstream end of said main conduit, and means forventing said conduit, the improvement comprising shunting means forrising undissolved gas in blood in said angularly disposed lower sectionand defined by a bypass conduit connected in parallel with said gasstripping chamber across said interconnecting section, said bypassconduit having an upstream end with a downstream-facing opening in theupper of said angularly disposed sections to facilitate transfer ofbubbles from the lower to the upper of said angularly disposed sectionsto provide blood flow in said bypass conduit at a rate different fromthe rate of flow in said gas stripping chamber, to prevent trapping ofrising undissolved gas in said interconnecting section.

2. A combination according to claim 1 in which the bypass conduit has adownstream end with a downstreamfacing opening in the lower of saidangularly disposed sections to facilitate entry of undissolved gas fromdownstream of said last opening into said bypass conduit.

3. A combination according to claim 1 in which each of said angularlydisposed sections has upper and lower walls, said bypass conduit beingS-shaped with opposite References Cited UNITED STATES PATENTS 3,058,46410/1962 Broman 23-258.5 3,087,490 4/1963 Broman 23-2585 6 3,101,0838/1963 Hyman 23-2585 3,112,746 12/1963 Gewecke et a1. 23-2585 3,374,0663/1968 Farrant 23258.5

FOREIGN PATENTS 965,376 7/ 1964 Great Britain.

MORRIS O. WOLK, Primary Examiner B. S. RICHMAN, Assistant Examiner

